(1) Field of the Invention
The present invention relates to an allyl ester oligomer composition which can be used as a spectacle material or an optical material for an optical disc, an optical fiber, a prism or the like, and to an organic glass having a relatively high refractive index and a high impact resistance, which is valuable for use as an optical material.
(2) Description of the Related Art
Since an organic glass has a lighter weight than an inorganic glass, an organic glass composed of a polymer of diethylene glycol bis(allylcarbonate) (hereinafter referred to as "CR-39") or methyl methacrylate is used. Nevertheless, the refractive index of the organic glass is 1.49 to 1.50 and is lower than that of the inorganic glass (the refractive index of white crown glass is 1.523), and accordingly, the thickness must be increased compared with the case of the inorganic glass, and thus the advantage of a reduction of the weight is lost, and when the organic lens is used for a sight-correcting lens, the organic lens is defective in that the appearance becomes poor with increase of the diopter.
As the means for coping with this disadvantage, various organic glasses formed by using a diallyl phthalate type monomer have been proposed, but these glasses are brittle or have a poor transmittance. If the diallyl phthalate type monomer is diluted with a monofunctional polymerizable monomer, to eliminate this defect, the heat resistance and solvent resistance become poor and the product is not satisfactory as an organic glass.
There is also known an allyl ester having terminal allyl ester groups and having in the interior thereof the following structure derived from a polybasic saturated carboxylic acid and a polyhydric saturated alcohol: EQU CH.sub.2 .dbd.CHCH.sub.2 O(CORCOOBO).sub.n CORCOOCH.sub.2 CH.dbd.CH.sub.2
wherein R represents an organic residue derived from the polybasic saturated carboxylic acid, and B represents an organic residue derived from the polyhydric saturated alcohol.
In this case, especially when terephthalic acid or isophthalic acid is used as the polybasic saturated carboxylic acid, the refractive index is relatively high and the impact resistance is high. Nevertheless, the viscosity is very high and a cast polymerization used for CR-39 cannot be adopted. Trials have been made to overcome this defect by diluting the above allyl ester with various monofunctional polymerizable monomers, but in these cases, the heat resistance and solvent resistance become poor and an organic glass having a satisfactory performance cannot be provided.